Semiconductor device and production method therefor

ABSTRACT

An object of the invention is to provide a method for producing a conductive member having low electrical resistance, and the conductive member is obtained using a low-cost stable conductive material composition that does not contain an adhesive. A method for producing a semiconductor device in which silver or silver oxide provided on a surface of a base and silver or silver oxide provided on a surface of a semiconductor element are bonded, includes the steps of arranging a semiconductor element on a base such that silver or silver oxide provided on a surface of the semiconductor element is in contact with silver or silver oxide provided on a surface of the base, and bonding the semiconductor element and the base by applying heat having a temperature of 200 to 900° C. to the semiconductor device and the base.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending application Ser. No.12/691,999 filed on Jan. 22, 2010, which claims priority under 35 U.S.C.§119(a) to Patent Application No. 2009-013712 filed in Japan on Jan. 23,2009. The entire contents of each of these applications are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device and a productionmethod therefor, especially, a method for bonding a semiconductorelement (hereinafter sometimes referred to as a “die-attach method”).

2. Description of Related Art

Various bonding methods for mounting semiconductor elements such astransistors, ICs, and LSIs have been known. In addition, various bondingmethods that are suitable with, among semiconductor elements, lightemitting semiconductor elements such as light emitting diodes(hereinafter sometimes referred to as “LEDs”) and laser diodes(hereinafter sometimes referred to as “LDs”) have been know as well.

Conventionally, die-attach methods for semiconductor elements areroughly classified into two categories, i.e., bonding methods that useepoxy resin adhesives (hereinafter referred to as “resin bonding”) andbonding methods that use eutectic metals having an eutectic point at ahigh temperature of 300° C. or greater (hereinafter referred to as“eutectic bonding”) (see, for example, Patent Documents 1 and 2). Suchdie-attach methods are selected according to the similarity between thethermal expansion behaviors of a lead frame material and a substratematerial on which a semiconductor element is to be mounted, as well asthe reliability, cost, and like factors. For example, resin bonding isused for light emitting diodes for use in liquid-crystal back lights ofsmall portable devices and like devices whose cost is given priority,and eutectic bonding is generally used for light emitting diodes forlighting purposes that are required to last a long time and for laserdiodes that are required to be highly reliable.

A resin for use in resin bonding is mostly a thermosetting resin such asan epoxy resin. A paste in which a powder of a conductive material suchas silver is dispersed is also a type of resin for resin bonding. Inresin bonding, a liquid epoxy resin is heated to 150 to 200° C. forcuring. Resin bonding is convenient in that curing can be readilyaccomplished at low temperatures of 150 to 200° C. In particular,thermal degradation of the thermosetting resin and melting of thethermoplastic resin can be avoided in a general-purpose surface-mountedsemiconductor device in which a lead frame is molded in advance.

However, the heat generation due to the recent increase of light energyattained by light emitting diodes, laser diodes and like devices as wellas the recent increase in input electricity, causes the resin itselfthat is used in resin bonding to deteriorate with time, resulting inproblems such as discoloration and deterioration of the bondingstrength. The glass transition temperature, which is an indicator interms of temperature of the modulus of elasticity of a resin, is,because curing is performed at a low temperature, lower than the soldermounting temperature applied when a semiconductor device is mounted asan electronic component, and thus separation resulting fromdeterioration of the resin strength caused by thermal shock duringsolder mounting is likely to occur. Moreover, resin bonding that usesonly an epoxy resin and resin bonding that uses a silver paste both havea problem in that, since they have poor thermal conductivity andinsufficient heat releasability, light emitting diodes and the likebecome unilluminable.

On the other hand, eutectic bonding that uses an alloy of gold and tincan solve the aforementioned problems of resin bonding.

However, eutectic bonding requires heating to 300° C. or greater whenbonding, and is therefore not applicable to widely used resin packagesof PPA (polyphthalamide) or the like since such packages cannotwithstand high temperatures. In addition, even if silver plating, whichhas high light reflectivity, is provided over the surface of a wiringboard or a lead frame on which a light emitting diode is to be mounted,light extraction effect cannot be enhanced since eutectic metals havepoor reflectivity.

Patent Document 1: JP 2004-128330 A

Patent Document 1: JP 2006-237141 A

SUMMARY OF THE INVENTION

Therefore, with the foregoing in mind, it is an object of the presentinvention to provide a method for mounting a reliable semiconductorelement and to provide a method for mounting a semiconductor elementthat has high heat releasability. Accordingly, a low-cost semiconductordevice and a simple production method of a semiconductor device can beprovided.

The present invention relates to a method for producing a semiconductordevice in which silver or silver oxide provided on a surface of a baseand silver or silver oxide provided on a surface of a semiconductorelement are bonded, the method includes the steps of arranging thesemiconductor element on the base such that silver or silver oxideprovided on a surface of the semiconductor element is in contact withsilver or silver oxide provided on a surface of the base, and bondingthe semiconductor element and the base by applying heat having atemperature of 200 to 900° C. to the semiconductor device and the base.It is thus possible to provide a method for producing a reliablesemiconductor device since components that are likely to deteriorate arenot used. Moreover, since the semiconductor element and the base aredirectly bonded, the thermal conductivity is high and the heat generatedby the semiconductor element can be efficiently transferred to the base.Furthermore, the semiconductor element can be mounted without specialequipment, so a simple production method for a semiconductor device canbe provided.

While a resin adhesive, a silver paste, a eutectic metal, or the like ispresent between the base and the semiconductor element in conventionalbonding such as resin bonding and eutectic bonding, the base and thesemiconductor element are directly bonded in the present invention. Aeutectic component that uses an alloy of gold and tin or a componentsuch as an epoxy resin or a silver paste is not present between thesemiconductor element and the base, and it is thus possible to provide areliable semiconductor device.

The temperature for the bonding is preferably in a range of 200 to 400°C., and more preferably in a range of 250 to 350° C.

It is preferable that the method further includes the step of applyingan organic solvent or water between the silver or silver oxide providedon a surface of the semiconductor element and the silver or silver oxideprovided on a surface of the base.

The organic solvent preferably has a boiling point of 100 to 300° C.

The step of bonding is preferably performed in air or in an oxygenenvironment.

A light emitting semiconductor element can also be used for thesemiconductor element.

The semiconductor element used may be a semiconductor element in which asemiconductor layer is disposed on a translucent inorganic substrate,the translucent inorganic substrate is provided with first silver on theside opposite the semiconductor layer and furnished with a bufferingmember bonded with the first silver, and the aforementioned silver orsilver oxide is provided on a surface of the buffering member.

By adopting the above-described configuration, a low-cost reliablesemiconductor device that does not include components that undergodeterioration and a production method therefor can be provided.Moreover, since the semiconductor element and the base can be directlybonded, a semiconductor device with high heat releasability can beprovided. Furthermore, a simple production method for a semiconductordevice can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional drawing showing the semiconductorlight emitting element of the first embodiment when mounted.

FIG. 2 is a schematic cross-sectional drawing showing the semiconductorlight emitting element of the second embodiment when mounted.

FIG. 3 is a schematic cross-sectional drawing showing the semiconductorlight emitting element of the third embodiment when mounted.

DETAILED DESCRIPTION OF THE INVENTION

The inventors found that when a composition containing silver particleshaving an average particle diameter of 0.1 to 15 μm is sintered in thepresence of a metal oxide or in an oxygen or ozone environment or inair, which serves as an oxidizer, silver particles are fused even at atemperature, for example, near 150° C. and a conductive material can beobtained. In contrast, when a composition containing silver particleshaving an average particle diameter of 0.1 to 15 μm is sintered in anitrogen environment, no conductive material was obtained at a lowtemperature near 150° C. Based on these findings, the inventorsaccomplished a method for producing a conductive material that includesthe step of sintering a composition containing silver particles havingan average particle diameter of 0.1 to 15 μm in the presence of a metaloxide or in an oxygen or ozone environment or in air, which serves as anoxidizer.

Furthermore, the inventors, during the process of investigating themechanism of the present invention in detail, performed low-temperaturebonding of smoothed silver-sputtered surfaces in the presence of oxygento examine the bondability of silver surfaces that are not organicallycontaminated, and found that, even if silver particles are not used,sufficient bonding can be attained by applying heat having a temperatureof 200° C. or greater. The inventors applied this finding to develop ahighly reliable semiconductor device and have arrived at the presentinvention. The inventors found at the same time that it is useful alsoas a method for providing a low-cost semiconductor device.

In the die-attach method of the present invention, the mechanism of bondformation is not clear, but it can be presumed to be as follows. Whensilver-coated surfaces formed by silver sputtering, silver vapordeposition, silver plating, or a like technique are brought into contactin an oxygen or ozone environment or in air that serves as an oxidizer,some portions of the silver-coated surfaces are locally oxidized, andthe silver oxide formed by the oxidation exchanges oxygen in acatalyst-like manner at the places of contact on the silver coatedsurfaces, and through repetitive redox reactions, bonds are formed.Moreover, it is also presumed that bonds are formed through the samemechanism also in an inert gas atmosphere by forming silver oxide inadvance by oxidizing the silver-coated surfaces. Bonds are presumablyformed through such a mechanism, and it is therefore possible to providea highly reliable low-cost semiconductor device when a semiconductordevice is produced according to the die-attach method of the presentinvention.

The present invention relates to a method for producing a semiconductordevice in which silver or silver oxide provided on a surface of a baseand silver or silver oxide provided on a surface of a semiconductorelement are bonded, and the method includes the steps of arranging thesemiconductor element on the base such that silver or silver oxideprovided on a surface of the semiconductor element is in contact withsilver or silver oxide provided on a surface of the base and bonding thesemiconductor element and the base by applying heat having a temperatureof 200 to 900° C. to the semiconductor device and the base. Theproduction method of the present invention can impart high emissionefficiency to a semiconductor device that uses a light emittingsemiconductor element such as a light emitting diode and a laser diode.Since no bonding material is interposed, low electrical resistance andlow thermal resistance are attained, and it is thus possible to provideenhanced reliability. Moreover, since bonding can be performed in thesame temperature range as in resin bonding, thermal deterioration of theplastics components used in the semiconductor device can be avoided.Since no resin is used in the bonding components, the life of thesemiconductor device is extended. Furthermore, since the productionprocess is simple and the amount of noble metal used is extremely low, asemiconductor device can be produced inexpensively.

An organic or inorganic substrate furnished with a lead frame ormetallic wiring can be used as the base, and the surface of the leadframe or the surface of the metal wiring is coated with silver. A silveroxide surface can be attained by oxidizing the entire base or a part ofthe base on which a semiconductor element is to be mounted. Irrespectiveof conductive portions or insulative portions, the surface to be bondedof the semiconductor element is silver-coated as with the base. Thesilver coating of the surface can be converted, as with the base, intosilver oxide by subjecting it to oxidizing treatment.

A temperature of 200 to 900° C. is applied to the base and thesemiconductor element to increase the number of bonding points and tomutually diffuse silver, thereby enabling strong bonding to be attained.Metal diffusion is obtained as a function of temperature, and thus, thehigher the temperature, the faster the enhancement of bonding strength,but to avoid the oxidative degradation or the melting of plasticcomponents used in the semiconductor device it is desirable to set theupper limit near 350° C., below which general-purpose thermoplasticresins do not melt. Note that, when a ceramics substrate or the likethat is heat resistant is used for the base, the temperature can beincreased to nearly 400° C. For the lower-limit temperature, 200° C. ora higher temperature is needed to obtain strong bonding within apractical time span.

Heating to 200° C. or greater is needed to attain bonding merely bymounting. The upper limit may be 900° C., which is below the meltingpoint of silver. However, the semiconductor device itself may sometimesbe destroyed at temperatures exceeding 400° C., and the upper limitpreferably is therefore 350° C. Hence, although the semiconductorelement and the base can be bonded by applying heat having a temperatureof to 200 to 400° C. to the semiconductor element and the substrate, itis preferable to apply heat having a temperature of 250 to 340° C.

It is preferable that the method further includes the step of applyingan organic solvent or water between the silver or silver oxide providedon a surface of the semiconductor element and the silver or silver oxideprovided on a surface of the base. Before the semiconductor element ismounted on the base, an organic solvent or water may be applied to thebase and then the semiconductor element may be mounted thereon. It isthereby possible due to the surface tension of the organic solvent orwater to keep the mounted semiconductor element accurately positioneduntil the subsequent bonding step.

The organic solvent preferably has a boiling point of 100 to 300° C.This is because an organic solvent having a boiling point of 100° C. orgreater does not easily evaporate and the mounted semiconductor elementcan readily be kept accurately positioned. The boiling point preferablyis lower than the heating temperature because organic solvent remainingafter the subsequent bonding step results in defective bonding, and theboiling point is thus specified as 300° C. or less to promptlyvolatilize it without thermal decomposition.

For the present invention, the step of bonding is preferably performedin air or in an oxygen environment. Thereby, an increase in the numberof bonding points and, hence, an enhancement of bonding strength can beexpected. In particular, the bonding environment for silver-silverbonding is preferably an oxidizing environment containing oxygen orozone, and more preferably air, which is inexpensive. In the case ofsilver-silver oxide bonding or silver oxide-silver oxide bonding, aninert gas environment that does not contain oxygen or ozone may be used,and a nitrogen environment, which is inexpensive, is preferable.

The bonding step is not necessarily composed of a single stage, and maybe composed of multiple stages in which the temperature is graduallyincreased or repetitively increased and decreased.

The semiconductor element used may be a semiconductor element in which asemiconductor layer is disposed on a translucent inorganic substrate,the translucent inorganic substrate is provided with first silver on theside opposite the semiconductor layer and furnished with a bufferingmember bonded with the first silver, and the aforementioned silver orsilver oxide is provided on a surface of the buffering member.

The present invention relates to a semiconductor device having a dieshear strength of 13 to 55 MPa in which silver or silver oxide providedon a surface of a base and silver or silver oxide provided on a surfaceof a semiconductor element are directly bonded. The die shear strengthis dependent on the heating temperature and the heating time duringbonding, and the higher the temperature and the longer the time, thehigher the strength, but the lower the temperature and the shorter thetime, the more advantageous it is when the production costs and theoxidative degradation of plastic components used in the semiconductordevice are taken into consideration. Therefore, the die shear strengthcan be controlled by selecting a heating temperature of 200 to 900° C.,preferably 250 to 400° C., and more preferably 250 to 350° C., andsuitably selecting a heating time. Practically, the semiconductor deviceneeds to withstand a ultrasonic shock during wire bonding and a thermalshock test performed thereon, and a die shear strength of 13 MPa orgreater is required, and the upper limit is preferably 55 MPa at whichthe die shear strength reaches saturation during bonding performed byheating at 350° C. To secure the reliability of the semiconductor deviceand to lessen the deterioration of the initial properties thereof thedie shear strength is more preferably 13 MPa to 35 MPa.

A light emitting semiconductor element can be used for the semiconductorelement. Silver reflects more visible light than any other metal, andproviding a silver coating on a surface of the semiconductor elementalso serves to furnish the semiconductor element with a high-efficiencyreflector, creating a configuration highly suitable in a light emittingsemiconductor element. Moreover, providing a silver coating on a surfaceof the base allows the entire semiconductor device to have areflector-like structure, and it is thus possible to extract light evenmore efficiently. The translucent inorganic substrate used in the lightemitting semiconductor element, since it absorbs very little light, cancontribute to producing a light emitting semiconductor element that hasa high emission efficiency. In the light emitting semiconductor element,a light emitting layer that is a semiconductor layer is formed on theupper surface of the translucent inorganic substrate, the light emittingsemiconductor element is arranged such that the light emitting layerbecomes the upper surface, and the under surface on the opposite side ofthe translucent inorganic substrate is provided with silver or silveroxide. It is thus possible to highly efficiently reflect the lightemitted from the light emitting layer and to obtain a semiconductordevice having a large emission intensity.

In the semiconductor element, the semiconductor layer is disposed on thetranslucent inorganic substrate, and the translucent inorganic substrateis provided with first silver on the side opposite the semiconductorlayer and furnished with a buffering member that is bonded with thefirst silver. A buffering member on a surface of which is provided withsilver or silver oxide may be used. Formation of the first silverbetween the outermost silver or silver oxide and the translucentinorganic substrate can enhance the light reflectivity and thus enhancethe emission intensity of the semiconductor device. One or more layersof the buffering member are provided between the first silver and theoutermost silver or silver oxide. Various buffering members can beselected according to the material of the base and the material of thetranslucent inorganic substrate, and various inorganic materials andvarious organic materials can be used. Use of the buffering memberreduces or alleviates the stress generated between the translucentinorganic substrate and the base, and it is thus possible to enhancebonding reliability and prevent cracks in the translucent inorganicsubstrate.

Semiconductor Device

Semiconductor Device of the First Embodiment

An example of the semiconductor device of the first embodiment isdescribed with reference to a drawing. FIG. 1 is a schematiccross-sectional drawing showing the semiconductor light emitting elementof the first embodiment when mounted. A description is given withreference to a light emitting semiconductor element that uses a lightemitting diode as a semiconductor element, but the present invention isapplicable also to transistors, ICs, LSIs, and the like other than lightemitting semiconductor elements.

In the semiconductor device, silver or silver oxide 520 provided on asurface of a base 500 and silver or silver oxide 140 provided on asurface of a light emitting semiconductor element 100 are directlybonded.

The light emitting semiconductor element 100 includes a translucentinorganic substrate 110, a semiconductor layer 120 that emits light, anelectrode 130 disposed on the semiconductor layer 120, first silver 150provided on the side opposite the side on which the semiconductor layer120 is disposed, a buffering member 160 bonded with the first silver,and the silver or silver oxide 140 provided on a surface of thebuffering member. In the semiconductor layer 120, an n-typesemiconductor layer 121 is stacked on the translucent inorganicsubstrate 110 and a p-type semiconductor layer 122 is stacked on then-type semiconductor layer 121. In the electrode 130, an n-typeelectrode 131 is disposed on the n-type semiconductor 121, and a p-typeelectrode 132 is disposed on the p-type semiconductor 122. The lightemitting semiconductor element 100 employs a flip chip structure thathas the n-type electrode 131 and the p-type electrode 132 on the sameside. One or more layers of the silver or silver oxide 140 may beprovided on a surface of the light emitting semiconductor element 100.Moreover, the thickness of the silver or silver oxide 140 provided on asurface of the light emitting semiconductor element 100 is notparticularly limited, but preferably is about 0.1 to 50 μm. It ispreferable to provide the first silver 150 to efficiently reflect thelight of the semiconductor layer 120. The thickness of the first silver150 can be suitably selected insofar as 85% or greater and preferably90% or greater of light can be reflected, e.g., 0.05 μm or greater.

The buffering member 160 can reduce or alleviate the bonding stressgenerated due to the difference between the mechanical properties of thetranslucent inorganic substrate 110 and the base 500. Various inorganicmaterials and organic materials can be used for the buffering member160, and multiple layers of such materials may be formed. A greatreduction in the stress that is generated during bonding can be expectedwith the use of an organic polymeric material for the buffering member160. Lest the exposed end portions of the buffering member 160 undergophotodegradation, an inorganic material is more preferable.

The silver or silver oxide 140 can be disposed below the bufferingmember 160, thereby allowing it to be bonded with the silver or silveroxide 520 provided on a surface of the base 500. For the silver andsilver oxide 140, use of silver oxide allows bonding to be accomplishedin an inert gas environment. Moreover, use of silver oxide can preventsulfuration and give storage stability to the light emittingsemiconductor element before being bonded. Silver oxide can be providedin such a manner that, first, silver is applied to the buffering member160 and then oxidized by oxygen plasma, UV irradiation, or a liketechnique, thereby giving silver oxide.

Note that, the silver or silver oxide 140 may be provided directly onthe translucent inorganic substrate 110. Furthermore, the silver orsilver oxide 140 is not necessarily provided in the form of a singlelayer and may be provided in the form of multiple layers composed of twoor more layers. Using the silver or silver oxide 140 in differentthicknesses or compositions, the bondability with the translucentinorganic substrate 110 can be enhanced.

In the base 500, the silver or silver oxide 520 is provided on a surfaceof a pedestal 510. The pedestal 510 may be conductive or insulative. Anexample of a conductive member used for the pedestal 510 includes a leadframe made of copper, iron, or a like material. If silver is used forthe pedestal 510, it is not necessary to provide the silver or silveroxide 520 and the pedestal 510 serves as the base 500.

On the other hand, examples of an insulative member used for thepedestal 510 include a glass epoxy board, a resin component such aspolyphthalamide or a liquid-crystal polymer, a ceramics component, and alike material. In the case where such an insulative member is used forthe pedestal 510, desired circuit wiring is installed on a glass epoxyboard and the silver or silver oxide 520 is provided on the circuitwiring.

For the silver and silver oxide 520 to be disposed on the pedestal 510,use of silver oxide allows bonding to be accomplished in an inert gasenvironment. Silver oxide can be provided in such a manner that, first,silver is applied to the pedestal 510 and then oxidized by oxygenplasma, UV irradiation, or a like technique, thereby giving silveroxide. Only a portion on which the light emitting semiconductor element100 is to be mounted may be oxidized. Silver oxide can be provided insuch a manner that, first, silver is applied to the buffering member 160and then oxidized by oxygen plasma, UV irradiation, or a like technique,thereby giving silver oxide.

The base 500 can take a variety of shapes such as a flat plate shape anda cup shape. For the ease of mounting the light emitting semiconductorelement 100, a base 500 in the shape of a flat plate is preferable. Toenhance the efficiency of extracting light from the light emittingsemiconductor element 100, the base 500 can take the shape of a cup. Inthe case where the base 500 is cup-shaped, part of the conductive wiringcan be exposed exterior of the base 500 as a terminal. Semiconductorlight emitting elements having the same function and semiconductorelements having different functions can be mounted on the base 500. Anelectronic element such as a resistive element and a capacitor may alsobe mounted on the base 500.

Wiring with a gold wire or the like is provided on the electrode 130disposed on the light emitting semiconductor element 100 to attain adesired electrical connection. The light emitting semiconductor element100 is encapsulated in an encapsulating member that contains afluorescent material, a filler, a light diffusing member, or the likethat absorbs the light emitted from the light emitting semiconductorelement 100 and converts the wavelength thereof into a differentwavelength, thereby giving a semiconductor device.

Method for Producing Semiconductor Device

The light emitting semiconductor element 100 is mounted on the base 500such that the silver or silver oxide 140 provided on a surface of thelight emitting semiconductor element 100 is brought into contact withthe silver or silver oxide 520 provided on a surface of the base 500. Nosolder, resin, or the like is present between the silver or silver oxide520 provided on a surface of the base 500 and the silver or silver oxide140 provided on a surface of the light emitting semiconductor element100. In the base 500, the pedestal 510 is provided with desired circuitwiring, and the silver or silver oxide 520 is provided on the outermostsurface of the circuit wiring. In connection with the positioning of thelight emitting semiconductor element 100, the circuit wiring may havevarious shapes, for example, circuit wiring having a shape identical tothe contour of the light emitting semiconductor element 100 can beformed, circuit wiring having a shape slightly smaller than butapproximately identical to the contour of the light emittingsemiconductor element 100 can be formed, or approximately square circuitwiring whose vertices extend to the four corners of the light emittingsemiconductor element 100 can be formed.

The light emitting semiconductor element 100 and the base 500 are bondedby applying heat having a temperature of 200 to 900° C. to the lightemitting semiconductor element 100 and the base 500. The temperatureapplied to the light emitting semiconductor element 100 and the base 500preferably is 250° C. or greater at which strong bonding can beattained. The temperature is not particularly limited insofar as thelight emitting semiconductor element 100 can withstand the heat, and itmay be no greater than 900° C., which is lower than the melting point ofsilver, and no greater than 400° C. or less is preferable. Moreover, atemperature of no greater than 350° C., which the light emittingsemiconductor element 100 and a packaging can withstand, is particularlypreferable. The bonding step can be performed also in air or in anoxygen environment. In the case where the silver 140 is used on asurface of the light emitting semiconductor element 100 and the silver520 is used on a surface of the base 500, bonding is performed in anoxygen environment. In the case where the silver 140 is used on asurface of the light emitting semiconductor element 100 and the silveroxide 520 is used on a surface of the base 500 and in the case where thesilver oxide 140 is used on a surface of the light emittingsemiconductor element 100 and the silver or silver oxide layer 520 isused on a surface of the base 500, bonding in both cases can beperformed in an inert gas environment such as a nitrogen environment,and it can be performed also in air or in an oxygen environment.Although a longer duration is more preferable, the necessary duration ofthe step of bonding is also not particularly limited and about 30minutes to 24 hours is sufficient.

Note that, since the melting point of silver is 961° C., sintering isperformed in the present production process at a temperature of nogreater than 900° C., which is lower than the melting point of silver,and a temperature of 200 to 400° C. in particular is a very lowtemperature.

After the light emitting semiconductor element 100 is mounted on thebase 500, wires are connected and encapsulation in an encapsulatingmember is performed, thereby giving a semiconductor device.

Semiconductor Device of the Second Embodiment

An example of the semiconductor device of the second embodiment isdescribed with reference to a drawing. FIG. 2 is a schematiccross-sectional drawing showing the semiconductor light emitting elementof the second embodiment when mounted. The semiconductor device of thesecond embodiment has substantially the same configuration as thesemiconductor device of the first embodiment except for the lightemitting semiconductor element, and some descriptions may be omitted.

In the semiconductor device, silver or silver oxide 620 provided on asurface of a base 600 and silver or silver oxide 240 provided on asurface of a light emitting semiconductor element 200 are bonded.

The light emitting semiconductor element 200 includes a translucentinorganic substrate 210, a semiconductor layer 220 that emits light, ap-type electrode 232 disposed on the semiconductor layer 220, firstsilver 250 provided on the side opposite the side on which thesemiconductor layer 220 is disposed, a buffering member 260 bonded withthe first silver 250, and the silver or silver oxide 240 provided on asurface of the buffering member 260. The bottom part of the translucentinorganic substrate 210 serves as an n-type electrode. In thesemiconductor layer 220, an n-type semiconductor layer 221 is stacked onthe translucent inorganic substrate 210 and a p-type semiconductor layer222 is stacked on the n-type semiconductor layer 221. The light emittingsemiconductor element 200 includes the n-type electrode on thelower-surface side (bottom part of the translucent inorganic substrate210) and the p-type electrode 232.

In the base 600, the silver or silver oxide 620 is provided on aconductive or insulative pedestal 610.

In this manner, even for the light emitting semiconductor element 200,which has such a configuration that the electrodes are disposed on theupper and lower surfaces, the silver or silver oxide layer 620 providedon the base 600 can be firmly bonded under specific conditions with thesilver or silver oxide layer 240 by providing the silver or silver oxidelayer 240 on the outermost lower surface of the light emittingsemiconductor element 200 on which mounting is performed.

Semiconductor Device of the Third Embodiment

An example of the semiconductor device of the third embodiment isdescribed with reference to a drawing. FIG. 3 is a schematiccross-sectional drawing showing the semiconductor light emitting elementof the third embodiment when mounted. The semiconductor device of thesecond embodiment have substantially the same configuration as thesemiconductor device of the first embodiment except for the lightemitting semiconductor element, and some descriptions may be omitted.

In the semiconductor device, silver or silver oxide 720 provided on asurface of a base 700 and silver or silver oxide 340 provided on asurface of a light emitting semiconductor element 300 are bonded.

The light emitting semiconductor element 300 includes a translucentinorganic substrate 310, a semiconductor layer 320 that emits light, anelectrode 330 disposed on the semiconductor layer 320, and silver orsilver oxide 340 provided on the electrode 330. In the semiconductorlayer 320, an n-type semiconductor layer 321 is stacked on thetranslucent inorganic substrate 310 and a p-type semiconductor layer 322is stacked on the n-type semiconductor layer 321. In the electrode 330,an n-type electrode 331 is disposed on the n-type semiconductor layer321, and a p-type electrode 332 is disposed on the p-type semiconductorlayer 322. The light emitting semiconductor element 300 employs a flipchip structure that has the n-type electrode 331 and the p-typeelectrode 332 on the same side and is mounted facedown. The n-typeelectrode 331 and the p-type electrode 332 are both provided on theirsurfaces with silver or silver oxide 340. It is preferable that thesilver or silver oxide 340 covers the entire surfaces of the n-typeelectrode 331 and the p-type electrode 332, but the silver or silveroxide layer 340 may be applied only to the portion that is brought intocontact with the base 700. One or more layers of the silver or silveroxide 340 may be provided on a surface of the light emittingsemiconductor element 300. Moreover, the thickness of the silver orsilver oxide 340 provided on a surface of the light emittingsemiconductor element 300 is not particularly limited, and preferably isabout 0.1 to 50 μm. In order to mount the light emitting semiconductorelement 300 facedown, it is preferable to adjust the heights of then-type electrode 331 and the p-type electrode 332 such that thetranslucent inorganic substrate 310 is disposed approximately parallelto the base.

In the base 700, a desired circuit pattern is provided on an insulativemount 710, and the silver or silver oxide 720 is provided on the circuitpattern.

In this manner, even for the light emitting semiconductor element 300,which has such a configuration that the n-type electrode 331 and thep-type electrode 332 are disposed on the same side and is mountedfacedown, the silver or silver oxide layer 720 provided on the base 700can be firmly bonded under specific conditions with the silver or silveroxide layer 340 by providing the silver or silver oxide layer 340 on then-type electrode 331 and the p-type electrode 332. In particular, sinceno solder bumps are used, bonding can be achieved without creating ashort circuit even when the distance between the n-type electrode 331and the p-type electrode 332 is small.

The method for producing the semiconductor device of the thirdembodiment is also nearly the same as the method for producing thesemiconductor device of the first embodiment except that no step of wireconnection is needed after the bonding of the light emittingsemiconductor element 300 and the base 700.

Semiconductor Element

For the semiconductor element, in addition to light emittingsemiconductor elements such as light emitting diodes and laser diodes,transistors, ICs, LSIs, Zener diodes, capacitors, light receivingelements, and the like can be used.

In the light emitting semiconductor element, a semiconductor layer isstacked on an inorganic substrate. The inorganic substrate preferably istranslucent Sapphire, GaP, GaN, ITO, ZnO, inorganic glass, ceramics, andthe like can be used for the translucent inorganic substrate, and asemiconductor such as GaAlN, ZnS, ZnSe, SiC, GaP, GaAlAs, AIN, InN,AlInGaP, InGaN, GaN, or AlInGaN processed into a light emitting layer isused for the semiconductor layer. The structure of the semiconductor maybe a homostructure, a heterostructure, or a double heterostructure, thathas an MIS junction, a PIN junction, or a PN junction. Various emissionwavelengths, from ultraviolet light to infrared light, can be selectedaccording to the material of the semiconductor layer and the compositionof the mixed crystals thereof. The light emitting layer may have asingle quantum well structure or a multiple quantum well structure inthe form of a thin film that exhibits a quantum effect.

If outdoor use or use in a like environment is considered, a galliumnitride compound semiconductor preferably is used for a semiconductorlayer that can form a high-intensity light emitting semiconductorelement, and a gallium/aluminium/arsenic semiconductor layer and analuminium/indium/gallium/phosphorus semiconductor layer preferably areused to create red, and various semiconductors can be used depending onthe application.

In the case where a gallium nitride compound semiconductor is used forthe semiconductor layer, materials such as sapphire, spinel, SiC, Si,ZnO, and GaN are used for the translucent inorganic substrate. It ispreferable to use sapphire for the translucent inorganic substrate toproduce highly crystalline gallium nitride that can easily be massproduced. In the case where the light emitting semiconductor element isused facedown, the translucent inorganic substrate is required to havehigh translucency.

Although the electrode preferably is of a material that does not blocklight, a light blocking material can also be used. In the case where thelight emitting semiconductor element is provided with an n-typeelectrode and a p-type electrode on the same side, it is preferable thatthe p-type electrode is provided to occupy a large area of thesemiconductor layer.

In the case where the light emitting semiconductor element is providedwith an n-type electrode and a p-type electrode on the upper and lowersurfaces, it is preferable that the electrode on the side that isbrought into contact with the base is provided so as to occupy a largearea, and it is particularly preferable that the electrode is providedso as to occupy nearly the entire lower surface. The electrode on theside that is brought into contact with the base preferably is coveredwith silver or silver oxide.

The translucent p-type electrode may be formed as a thin film having athickness of 150 μm or less. Moreover, non-metal materials such as ITOand ZnO can also be used for the p-type electrode. Here, in place of thetranslucent p-type electrode, an electrode that has a plurality ofopenings for light extraction, such as a mesh electrode, may be used.

In addition to a linear shape, the electrode may take, for example, acurved, whisker, comb, lattice, branch, hook, or network shape. Thelight blocking effect is increased proportional to the total area of thep-type electrode, it is thus preferable to design the line width andlength of an extended conductive part such that the light emissionenhancing effect is not overwhelmed by the light blocking effect. Metalssuch as Au and Au—Sn as well as non-metal materials such as ITO and ZnOcan be used for the p-type electrode. In place of the translucent p-typeelectrode, an electrode that has a plurality of openings for lightextraction, such as a mesh electrode, may be used. The size of the lightemitting semiconductor element may be suitably selected.

The buffering member of the light emitting semiconductor elementpreferably contains at least one inorganic material, other than silverand silver oxide, selected from the group consisting of gold, copper,aluminium, tin, cobalt, iron, indium, tungsten and like metals as wellas alloys thereof; silica, alumina, zirconium oxide, titanium oxide, andlike oxides; and aluminium nitride, zirconium nitride, titanium nitride,and like nitrides. The buffering member of the light emittingsemiconductor element preferably contains at least one organic materialselected from the group consisting of an epoxy resin, a silicone resin,a modified silicone resin, a polyimide resin, and like insulativeresins; and conductive resins that are produced by filling suchinsulative resins with large amounts of metal powder.

If silver oxide is to be provided on the outermost surface of thesemiconductor element, silver is applied first and then oxidized byoxygen plasma, UV irradiation, or a like technique, thereby givingsilver oxide. The formation of silver oxide allows bonding to beachieved in an inert gas environment. The sulfuration of silver can beprevented.

Base

In the base, silver or silver oxide is provided on a surface of thepedestal. A ceramic substrate containing aluminium oxide, aluminiumnitride, zirconium oxide, zirconium nitride, titanium oxide, titaniumnitride, or a mixture of these, a metal substrate containing Cu, Fe, Ni,Cr, Al, Ag, Au, Ti, or an alloy of these, a lead frame, a glass epoxyboard, a BT resin substrate, a glass substrate, a resin substrate,paper, and the like can be used for the base. An example of the leadframe is a metal frame formed from copper, iron, nickel, chromium,aluminium, silver, gold, titanium, or an alloy of these, and a metalframe formed from copper, iron, or an alloy of these is preferable. Morepreferably, the lead frame is of a copper alloy in the case of asemiconductor device that needs to have heat releasability, and of aniron alloy in the case of a semiconductor device in which thesemiconductor element needs to be reliably bonded. In the case wheresilver or silver oxide is used in the portion corresponding to thepedestal of the base, it is not necessary to further provide silver orsilver oxide.

The surface of the wiring board or the lead frame may be coated withsilver, silver oxide, silver alloy, silver alloy oxide, Pt, Pt alloy,Sn, Sn alloy, gold, gold alloy, Cu, Cu alloy, Rh, Rh alloy, or the like,and the outermost surface of the portion on which the semiconductorelement is to be mounted is coated with silver or silver oxide. Coatingwith such materials can be performed by plating, vapor deposition,sputtering, printing, applying, or a like technique.

A resin package may be used for the base. A package in which a lead ismolded integrally and a package in which circuit wiring is created byplating or a like technique after package molding may be usable. Thepackage can take a variety of shapes such as a cup shape and a flatplate shape. An electrically insulative resin that has excellent lightresistance and heat resistance is suitably used for the resin that formsthe package and, for example, a thermoplastic resin such aspolyphthalamide, a thermosetting resin such as an epoxy resin, glassepoxy, and ceramics can be used. Moreover, to efficiently reflect thelight emitted from the light emitting semiconductor element, a whitepigment such as titanium oxide can be added to such resins. Usablemethods of package molding include insert molding in which a lead isplaced in advance in a metal mold, injection molding, extrusion molding,transfer molding, and the like.

Organic Solvent

The organic solvent may be any organic solvent insofar as it can fastenthe semiconductor element at ordinary temperatures and the residue ofwhich does not remain after heat bonding. The boiling point of theorganic solvent preferably is 100 to 300° C. and can be selectedaccording to the heating temperature during bonding. For example, atleast one member can be selected from the following group: lower andhigher alcohols containing an alkyl group having 2 to 10 carbon atoms(20 carbon atoms) and 1 to 3 hydroxyl groups (e.g., lower alcohols suchas n-butanol, i-butanol, sec-butanol, t-butanol, n-pentanol, i-pentanol,sec-pentanol, t-pentanol, 2-methyl butanol, n-hexanol, 1-methylpentanol, 2-methyl pentanol, 3-methyl pentanol, 4-methyl pentanol,1-ethyl butanol, 2-ethyl butanol, 1,1-dimethylbutanol,2,2-dimethylbutanol, 3,3-dimethylbutanol, 1-ethyl-1-methylpropanol, andthe like, and higher alcohols such as nonanol, decanol, and the like);2-ethyl-1,3-hexanediol, glycerol, ethylene glycol, diethylene glycol,diethylene glycol monobutyl ether, diethylene glycol monoethyl ether,triethylene glycol; hydrocarbon solvents and aliphatic solvents having 8to 20 carbon atoms (e.g., n-heptane, n-octane, n-nonane, n-decane,n-tetradecane, and the like); solvents containing a carboxyl group andan alkoxyl group (e.g., isopentyl acetate, 2-ethylhexyl acetate, ethylpropionate, and the like); aromatic solvents (e.g., toluene, xylene,anisole, phenol, aniline, monochlorobenzene, dichlorobenzene, and thelike); dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and thelike.

An oxidizing gas such as oxygen, hydrogen peroxide, or ozone that iscompletely volatilized and does not remain by heating may be dissolvedin the organic solvent or water. Thereby, the formation of silver oxideand the acceleration of bonding can be expected. Moreover, fineparticles having such a particle diameter that the particles do notserve as a spacer can also be added. Thereby, an enhancement of bondingstrength can be expected.

Encapsulating Member

An encapsulating member is used to protect the semiconductor devicemounted on the base from external forces, dust, etc. Also, theencapsulating member can let the light emitted from the light emittingsemiconductor element efficiently pass through outwardly. Examples ofresins used for the encapsulating member include an epoxy resin, aphenolic resin, an acrylic resin, a polyimide resin, a silicone resin, aurethane resin, a thermoplastic resin, and the like. In particular, asilicone resin is preferable since a long-lasting semiconductor devicethat has excellent heat resistance and light resistance can be produced.For an airtight cover or a non-airtight cover, inorganic glass, apolyacrylic resin, a polycarbonate resin, a polyolefin resin, apolynorbonene resin, and the like can be mentioned. In particular,inorganic glass is preferable since a long-lasting semiconductor devicethat has excellent heat resistance and light resistance can be produced.

Others

The encapsulating member may contain a fluorescent material, a filler, alight diffusing member, and the like. The fluorescent material may beany material that absorbs the light emitted from the light emittingsemiconductor element and emits a fluorescence having a wavelengthdifferent from that of the light, and preferably is at least one memberselected from a nitride phosphor or an oxynitride phosphor that isactivated primarily by a lanthanoid element such as Eu or Ce; analkaline earth halogen apatite phosphor, a halogenated alkaline earthmetal borate phosphor, an alkaline earth metal aluminate phosphor, analkaline earth silicate phosphor, an alkaline earth sulfide phosphor, analkaline earth thiogallate phosphor, an alkaline earth silicon nitridephosphor, and a germanate phosphor that are activated primarily by alanthanoid element such as Eu or a transition metal element such as Mn;a rare earth aluminate phosphor and a rare earth silicate phosphor thatare activated primarily by a lanthanoid element such as Ce; and organicand inorganic complexes that are activated primarily by a lanthanoidelement such as Eu; and the like. More preferably, (Y, Gd)₃(Al,Ga)₅O₁₂:Ce, (Ca, Sr, Ba)₂SiO₄:Eu, (Ca, Sr)₂Si₅N₈:Eu, CaAlSiN₃:Eu, andthe like are used.

For the filler, alumina, silica, tin oxide, zinc oxide, titanium oxide,magnesium oxide, silicon nitride, boron nitride, aluminium nitride,potassium titanate, mica, calcium silicate, magnesium sulfate, bariumsulfate, aluminium borate, glass flake, and glass fiber can be used. Inaddition, silicone rubber particles and silicone elastomer particles canbe used for stress relaxation. The light transmittance is greatlyinfluenced by the diameter of the filler particles, and the averageparticle diameter preferably is 5 μm or greater, but nanoparticles canalso be used. It is thus possible to greatly enhance the translucencyand light dispersibility of the encapsulating member.

For the light diffusing member, alumina, silica, tin oxide, zinc oxide,titanium oxide, magnesium oxide, silicon nitride, boron nitride,aluminium nitride, potassium titanate, mica, calcium silicate, magnesiumsulfate, barium sulfate, aluminium borate, glass flake, and glass fibercan be used. In addition, particles of thermosetting resins such as anepoxy resin, a silicone resin, a benzoguanine resin, and a melamineresin can be used. The light diffusibility is greatly influenced by thediameter of the filler particles, and the average particle diameterpreferably is in a range of 0.1 to 5 μm. It is thereby possible toattain light diffusion with a smaller amount of light diffusing member.

The semiconductor element can be coated with the fluorescent material,the filler, and the light diffusing member also by printing, potting,electrodeposition, and stamping. The encapsulating member can be appliedto the upper surface thereof. This makes optical design easy in the casewhere the encapsulating member has a lens shape and enables ahigh-quality semiconductor device to be obtained.

EXAMPLES

Below, the semiconductor device and the production method therefor ofthe present invention will be described by way of examples. Thesemiconductor devices of Example 1 to 8 are encompassed within thesemiconductor device of the first embodiment, and some descriptions maytherefore be omitted.

Example 1

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silver140, was used. For a base 500, a cup-shaped package was formed as apedestal 510, and silver 520 with which the surface of a lead frameexposed on the outside of the package was silver-plated was used. Thepackage was formed by arranging a lead frame that used copper as aprimary component on an epoxy resin in which a white pigment wasdispersed and subjecting it to insert molding.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver 140 of the light emitting semiconductor element 100 was directlyin contact therewith. Bonding was performed as follows: after mountingthe light emitting semiconductor element 100 the base 500 was heated inair at about 200° C. for about 3 hours. It was thus possible to directlybond the light emitting semiconductor element 100 and the base 500.

Example 2

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silver140, was used. For a base 500, a cup-shaped package was formed as apedestal 510, and silver 520 with which the surface of a lead frameexposed on the outside of the package was silver-plated was used. Thepackage was formed by arranging a lead frame that used copper as aprimary component on an epoxy resin in which a white pigment wasdispersed and subjecting it to insert molding.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver 140 of the light emitting semiconductor element 100 was directlyin contact therewith. Bonding was performed as follows: after mountingthe light emitting semiconductor element 100 the base 500 was heated inair at about 350° C. for about 30 minutes. It was thus possible todirectly bond the light emitting semiconductor element 100 and the base500.

Example 3

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silver140, was used. For a base 500, a cup-shaped alumina ceramics substratewas formed as a pedestal 510, and silver 520 with which the surface ofan underlying metal disposed on the alumina ceramics substrate wassilver-plated was used. The alumina ceramics substrate was formed bystacking alumina ceramics in the shape of a cup, providing an underlyingmetal thereon, sintering the alumina ceramics, and silver-plating thesurface of the underlying metal of the sintered alumina ceramics.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver 140 of the light emitting semiconductor element 100 was directlyin contact therewith. Bonding was performed as follows: after mountingthe light emitting semiconductor element 100 the base 500 was heated inair at about 200° C. for about 20 hours. It was thus possible todirectly bond the light emitting semiconductor element 100 and the base500.

Example 4

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silver140, was used. For a base 500, a cup-shaped alumina ceramics substratewas formed as a pedestal 510, and silver 520 with which the surface ofan underlying metal disposed on the alumina ceramics substrate wassilver-plated was used. The alumina ceramics substrate was formed bystacking alumina ceramics in the shape of a cup, providing an underlyingmetal thereon, sintering the alumina ceramics, and silver-plating thesurface of the underlying metal of the sintered alumina ceramics.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver 140 of the light emitting semiconductor element 100 was directlyin contact therewith. Bonding was performed as follows: after mountingthe light emitting semiconductor element 100 the base 500 was heated inair at about 350° C. for about 1 hour. It was thus possible to directlybond the light emitting semiconductor element 100 and the base 500.

Example 5

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silveroxide 140, was used. For a base 500, a cup-shaped package was formed asa pedestal 510, and silver 520 with which the surface of a lead frameexposed on the outside of the package was silver-plated was used. Thepackage was formed by arranging a lead frame that used copper as aprimary component on an epoxy resin in which a white pigment wasdispersed and subjecting it to insert molding.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver oxide 140 of the light emitting semiconductor element 100 wasdirectly in contact therewith. Bonding was performed as follows: aftermounting the light emitting semiconductor element 100 the base 500 washeated in a nitrogen stream at about 200° C. for about 4 hours. It wasthus possible to directly bond the light emitting semiconductor element100 and the base 500.

Example 6

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silveroxide 140, was used. For a base 500, a cup-shaped package was formed asa pedestal 510, and silver 520 with which the surface of a lead frameexposed on the outside of the package was silver-plated was used. Thepackage was formed by arranging a lead frame that used copper as aprimary component on an epoxy resin in which a white pigment wasdispersed and subjecting it to insert molding.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver oxide 140 of the light emitting semiconductor element 100 wasdirectly in contact therewith. Bonding was performed as follows: aftermounting the light emitting semiconductor element 100 the base 500 washeated in a nitrogen stream at about 350° C. for about 1 hour. It wasthus possible to directly bond the light emitting semiconductor element100 and the base 500.

Example 7

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silveroxide 140, was used. For a base 500, a cup-shaped alumina ceramicssubstrate was formed as a pedestal 510, and silver 520 with which thesurface of an underlying metal disposed on the alumina ceramicssubstrate was silver-plated was used. The alumina ceramics substrate wasformed by stacking alumina ceramics in the shape of a cup, providing anunderlying metal thereon, sintering the alumina ceramics, andsilver-plating the surface of the underlying metal of the sinteredalumina ceramics.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver oxide 140 of the light emitting semiconductor element 100 wasdirectly in contact therewith. Bonding was performed as follows: aftermounting the light emitting semiconductor element 100 the base 500 washeated in a nitrogen stream at about 200° C. for about 24 hours. It wasthus possible to directly bond the light emitting semiconductor element100 and the base 500.

Example 8

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silveroxide 140, was used. For a base 500, a cup-shaped alumina ceramicssubstrate was formed as a pedestal 510, and silver 520 with which thesurface of an underlying metal disposed on the alumina ceramicssubstrate was silver-plated was used. The alumina ceramics substrate wasformed by stacking alumina ceramics in the shape of a cup, providing anunderlying metal thereon, sintering the alumina ceramics, andsilver-plating the surface of the underlying metal of the sinteredalumina ceramics.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver oxide 140 of the light emitting semiconductor element 100 wasdirectly in contact therewith. Bonding was performed as follows: aftermounting the light emitting semiconductor element 100 the base 500 washeated in a nitrogen stream at about 350° C. for about 2 hours. It wasthus possible to directly bond the light emitting semiconductor element100 and the base 500.

Reference Example 1

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silver140, was used. For a base 500, a cup-shaped package was formed as apedestal 510, and silver 520 with which the surface of a lead frameexposed on the outside of the package was silver-plated was used. Thepackage was formed by arranging a lead frame that used copper as aprimary component on an epoxy resin in which a white pigment wasdispersed and subjecting it to insert molding.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver 140 of the light emitting semiconductor element 100 was directlyin contact therewith. Bonding was performed as follows: after mountingthe light emitting semiconductor element 100 the base 500 was heated ina nitrogen stream at about 190° C. for about 24 hours. It was thuspossible to directly bond the light emitting semiconductor element 100and the base 500.

Results of Measurement

The die shear strength of the semiconductor devices of Examples 1 to 8and Reference Example 1 was measured. For the measurement of die shearstrength, a shearing force was applied at room temperature in adirection stripping the light emitting semiconductor element 100 off thebase 500, and the intensity of the force when the light emittingsemiconductor element 100 was stripped off was determined. The resultsof the die shear strength (gf) measurement are presented in Table 1.

TABLE 1 Example Die shear strength (gf) Example 1 602.5 Example 2 525.3Example 3 501.2 Example 4 513.2 Example 5 511.5 Example 6 542.3 Example7 518.4 Example 8 580.6 Ref. Ex. 1 384.5

According to the results of the measurement, it was found that thehigher the temperature of the bonding, the shorter the time taken toattain the desired die shear strength. It was found that a practical dieshear strength can be obtained by selecting a temperature of 200° C. orgreater and a suitable heating time. Although the temperature of 350° C.was employed in view of the heat resistance of the package and the lightemitting semiconductor element, higher temperatures can be employed whena package and a semiconductor element of greater heat resistance areused. It was found that bonding can be accomplished in a nitrogen streamby providing silver oxide on the light emitting semiconductor elementside. Although not presented as an example, bonding can be similarlyaccomplished in a nitrogen stream in a semiconductor device in whichsilver oxide is provided on the base side.

On the other hand, although bonding was accomplished at a heatingtemperature of 190° C. in Reference Example 1, the die shear strengthwas not sufficient.

Note that, because of the difference between the thermal conductivitiesand other properties of the ceramics component used for the base and theepoxy resin, the time taken to achieve the desired die shear strengthmay sometimes be different even when the same temperature is applied.

Initial Properties

Comparative Example 1

Bonding was performed using the same components as in Example 3 exceptthat a clear colorless insulative epoxy resin was used as a die bondingcomponent in Comparative Example 1. Curing was performed at 170° C. for1 hour. The die shear strength attained in Comparative Example 1 wasabout 900 gf.

Comparative Example 2

Bonding was performed using the same components as in Example 3 exceptthat a silver paste containing 80 wt % of a flaky silver filler and 20wt % of an epoxy resin was used in Comparative Example 2. Curing wasperformed at 150° C. for 1 hour. The die shear strength attained inComparative Example 2 was about 1500 gf.

Results of Measurement

In connection with Example 3, Comparative Example 1, and ComparativeExample 2, the electrode of the light emitting semiconductor element andthe electrode of the base were gold-wired and encapsulated in a siliconeresin, thereby giving a semiconductor device. The emission intensity ofeach semiconductor device as-is was measured. The emission intensity ispresented as a value relative to the intensity obtained in Example 3being 100%. Table 2 shows the results of measurement.

TABLE 2 Relative intensity Bonding of emission (%) Ex. 3 Direct Agbonding 100 Comp. Ex. 1 Bonding with 94 insulative epoxy resin Comp. Ex.2 Bonding with flaky silver 84 filler-containing epoxy resin

As can be understood from the results of measurement, a semiconductordevice that had the highest emission intensity was obtained from Example3. It can be presumed that the emission intensity was lower inComparative Example 1 because the insulative epoxy resin formed a filletand, in addition, the color of the epoxy resin turned slightly yellowwhen cured. Similarly, it can be presumed that the intensity of emissionwas much lower in Comparative Example 2 because the flaky silverfiller-containing epoxy resin formed a fillet and, in addition, thecolor of the epoxy resin turned slightly yellow when cured and,simultaneously, light scattering due to the flaky silver filleroccurred.

Power-On Test

An electric current was applied to the semiconductor devices of Example3, Comparative Example 1, and Comparative Example 2 as-is (testconditions: 25° C. and 50 mA) for 500 hours, 1000 hours, and 2000 hours,and the emission intensity was then measured. Table 3 shows theintensity relative to the initial intensity.

TABLE 3 After 500 After 1000 After 2000 Bonding hours hours hours Ex. 3Direct Ag bonding 100% 99% 99% Comp. Ex. 1 Bonding with 95% 80% 60%insulative epoxy resin Comp. Ex. 2 Bonding with flaky 93% 75% 60% silverfiller-containing epoxy resin

It was demonstrated that the semiconductor device obtained in Example 3can maintain high emission intensity even after 2000 hours. On the otherhand, it was demonstrated that the semiconductor devices obtained inComparative Examples 1 and 2 exhibited severely impaired intensity after2000 hours.

Furthermore, it was demonstrated that no discoloration can be observedin the periphery of the light emitting semiconductor element of Example3 even after 2000 hours. On the other hand, it was demonstrated that thecolor of the clear colorless insulative epoxy resin of ComparativeExample 1 disposed for bonding between the light emitting semiconductorelement and the base as well as the fillet portions was dark reddishbrown after 2000 hours. Moreover, it was demonstrated that the color ofthe silver paste containing 80 wt % of a flaky silver filler and 20 wt %of an epoxy resin of Comparative Example 2 disposed for bonding betweenthe light emitting semiconductor element and the base as well as thefillet portions was dark reddish brown after 2000 hours.

Example 9

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silver140, was used. For a base 500, a cup-shaped package was formed as apedestal 510, and silver 520 with which the surface of a lead frameexposed on the outside of the package was silver-plated was used. Thepackage was formed by arranging a lead frame that used copper as aprimary component on an epoxy resin in which a white pigment wasdispersed and subjecting it to insert molding.

The light emitting semiconductor element 100 was mounted such that thesilver 140 thereof was directly in contact with the silver 520 of thebase 500. For this mounting, the lead frame was preheated to about 250°C. in air, and the light emitting semiconductor element 100 was mountedon the base 500. Bonding was performed as follows: the base 500 on whichthe light emitting semiconductor element 100 was mounted was heated inair at about 350° C. for about 10 minutes. It was thus possible todirectly bond the semiconductor light emitting element 100 and the base500 in a short time.

Example 10

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silver140, was used. For a base 500, a cup-shaped alumina ceramics substratewas formed as a pedestal 510, and silver 520 with which the surface ofan underlying metal disposed on the alumina ceramics substrate wassilver-plated was used. The alumina ceramics substrate was formed bystacking alumina ceramics in the shape of a cup, providing an underlyingmetal thereon, sintering the alumina ceramics, and silver-plating thesurface of the underlying metal of the sintered alumina ceramics.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver 140 of the light emitting semiconductor element 100 was directlyin contact therewith. Bonding was performed as follows: after mountingthe light emitting semiconductor element 100 the base 500 was heated atabout 150° C. for about 30 minutes, then heated at about 200° C. forabout 30 minutes, and further heated at about 350° C. for about 1 hourin air. It was thus possible to directly bond the light emittingsemiconductor element 100 and the base 500.

Example 11

For a light emitting semiconductor element 100, a translucent inorganicsapphire substrate 110 having the dimensions of 600 μm×600 μm×100 μm(thickness), on the upper surface of which was stacked a semiconductorInGaN layer 120 and the lower layer of which was metallized with silver140, was used. For a base 500, a cup-shaped alumina ceramics substratewas formed as a pedestal 510, and silver 520 with which the surface ofan underlying metal disposed on the alumina ceramics substrate wassilver-plated was used. The alumina ceramics substrate was formed bystacking alumina ceramics in the shape of a cup, providing an underlyingmetal thereon, sintering the alumina ceramics, and silver-plating thesurface of the underlying metal of the sintered alumina ceramics.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver 140 of the light emitting semiconductor element 100 was directlyin contact therewith. Bonding was performed as follows: after mountingthe light emitting semiconductor element 100 the base 500 was heated inair at about 420° C. for about 15 minutes. It was thus possible todirectly bond the light emitting semiconductor element 100 and the base500.

Example 12

For a semiconductor device 100, a Zener diode was used in place of asemiconductor light emitting element. For the semiconductor element 100,an Si substrate 110 having a dimension of 300 μm×300 μm×200 μm(thickness), on the upper surface of which was formed a semiconductorlayer 120 and the lower layer of which was metallized with silver 140,was used. For a base 500, a cup-shaped package was formed as a pedestal510, and silver 520 with which the surface of a lead frame exposed onthe outside of the package was silver-plated was used. The package wasformed by arranging a lead frame that used copper as a primary componenton an epoxy resin in which a white pigment was dispersed and subjectingit to insert molding.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver 140 of the semiconductor element 100 was directly in contacttherewith. Bonding was performed as follows: after mounting thesemiconductor element 100 the base 500 was heated in air at about 300°C. for about 1 hour. It was thus possible to directly bond thesemiconductor element 100 and the base 500. Use of a light emittingdiode and a Zener diode in one package allows them to be permanentlybonded simultaneously after accomplishing the temporary bonding of thelight emitting diode and the temporary bonding of the Zener diode, andit was thus possible to simplify the production process.

Example 13

For a semiconductor device 100, an IC chip was used in place of a lightemitting semiconductor element. For the semiconductor element 100, aninorganic Si substrate 110 having the dimensions of 300 μm×300 μm×200 μm(thickness), on the upper surface of which was formed a semiconductorlayer 120 and the lower layer of which was metallized with silver 140,was used. For a base 500, a plate-shape alumina ceramics substrate wasformed as a pedestal 510, and silver 520 with which the surface of anunderlying metal disposed on the alumina ceramics substrate wassilver-plated was used. The alumina ceramics substrate was formed bystacking alumina ceramics in the shape of a plate, providing anunderlying metal thereon, sintering the alumina ceramics, andsilver-plating the surface of the underlying metal of the sinteredalumina ceramics.

An organic solvent diethylene glycol monobutyl ether was applied to thesilver 520 of the base 500, and mounting was performed such that thesilver 140 of the semiconductor element 100 was directly in contacttherewith. Bonding was performed as follows: after mounting thesemiconductor element 100 the base 500 was heated in air at about 350°C. for about 30 minutes. It was thus possible to directly bond thesemiconductor element 100 and the base 500.

The method for producing a semiconductor device of the present inventionis applicable to, for example, the connection of component electrodes,die attaching, fine-pitch bumping, flat panels, solar wiring and likeproduction applications, and wafer connection and like applications aswell as to the production of electronic parts produced by assemblingsuch components. Moreover, the method for producing a semiconductordevice of the present invention is applicable when, for example,semiconductor devices that use light emitting semiconductor elementssuch as LEDs and LDs are produced.

Description Of Reference Numerals

100, 200, 300: Light emitting semiconductor element

110, 210, 310: Translucent inorganic substrate

120, 220, 320: Semiconductor layer

121, 221, 321: N-type semiconductor

122, 222, 322: P-type semiconductor

130, 330: Electrode

131, 331: N-type electrode

132, 232, 332: P-type electrode

140, 240, 340: Silver or silver oxide

150, 250: First silver

160, 260: Buffering member

500, 600, 700: Base

510, 610, 710: Pedestal

520, 620, 720: Silver or silver oxide

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof. The embodiments disclosedin this application are to be considered in all respects as illustrativeand not limiting. The scope of the invention is indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

What is claimed is:
 1. A method for producing a semiconductor device,the method comprising: for silver formed by silver sputtering, silvervapor deposition or silver plating and provided on a surface of a base,and silver formed by silver sputtering, silver vapor deposition orsilver plating and provided on a surface of a semiconductor element,arranging the semiconductor element on the base such that said silverprovided on the surface of the semiconductor element directly contactssaid silver provided on the surface of the base, and bonding thesemiconductor element and the base in an oxidizing environment oroxidizing atmosphere, by applying heat having a temperature of 200 to900° C. to the semiconductor element and the base.
 2. The method forproducing a semiconductor device according to claim 1, furthercomprising the step of applying an organic solvent or water between thesilver provided on the surface of the semiconductor element and thesilver provided on the surface of the base.
 3. The method for producinga semiconductor device according to claim 2, wherein the organic solventhas a boiling point of 100 to 300° C.
 4. The method for producing asemiconductor device according to claim 2, wherein the organic solventis at least one member selected from the group consisting of2-ethyl-1,3-hexanediol, glycerol, ethylene glycol, diethylene glycol,diethylene glycol monobutyl ether, diethylene glycol monoethyl ether,and triethylene glycol.
 5. The method for producing a semiconductordevice according to claim 1, wherein said oxidizing environment oroxidizing atmosphere is air or an oxygen environment.
 6. The method forproducing a semiconductor device according to claim 1, wherein thesemiconductor element is a light emitting semiconductor element.
 7. Themethod for producing a semiconductor device according to claim 6,wherein in the semiconductor element a semiconductor layer is disposedon a translucent inorganic substrate, the translucent inorganicsubstrate is provided with first silver on the side opposite thesemiconductor layer and furnished with a buffering member bonded withthe first silver, and the silver is provided on a surface of thebuffering member.
 8. The method for producing a semiconductor deviceaccording to claim 1, wherein, in said arranging step the semiconductorelement and the base are arranged such that said silver provided on thesurface of the semiconductor element directly contacts said silverprovided on the surface of the base, such that said silver provided onthe surface of the semiconductor element touches said silver provided onthe surface of the base.
 9. The method for producing a semiconductordevice according to claim 1, wherein, in said arranging step, thesemiconductor element and the base are arranged such that, at theinterface between said silver provided on the surface of thesemiconductor element, and said silver provided on the surface of thebase, said silver provided on the surface of the semiconductor elementdirectly contacts said silver provided on the surface of the base. 10.The method for producing a semiconductor device according to claim 1,wherein said bonding step is performed by applying heat having atemperature of 200 to 400° C. to the semiconductor element and the base.11. The method for producing a semiconductor device according to claim2, wherein said organic solvent or water is applied to the base beforethe semiconductor element is mounted on the base, thereafter, thesemiconductor element is mounted on the base, said mounted semiconductorelement being kept positioned on the base due to the surface tension ofsaid organic solvent or water, until said bonding step is performed, andsaid organic solvent or water is volatilized during the bonding step.12. The method for producing a semiconductor device according to claim1, wherein said oxidizing environment or oxidizing atmosphere contains asubstantial amount of oxygen.
 13. The method for producing asemiconductor device according to claim 1, wherein said oxidizingenvironment or oxidizing atmosphere contains a substantial amount ofozone.
 14. A method for producing a semiconductor device, the methodcomprising: for silver formed by silver sputtering, silver vapordeposition or silver plating and provided on a surface of a base, andsilver formed by silver sputtering, silver vapor deposition or silverplating and provided on a surface of a semiconductor element, arrangingthe semiconductor element on the base such that said silver provided onthe surface of the semiconductor element directly contacts said silverprovided on the surface of the base, and bonding the semiconductorelement and the base in an oxidizing environment or oxidizingatmosphere, by applying heat having a temperature of 200 to 900° C. tothe semiconductor element and the base, said method further comprisingthe step of applying an organic solvent or water between the silverprovided on the surface of the semiconductor element and the silverprovided on the surface of the base, wherein said organic solvent orwater is volatilized during the bonding step.